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What is a normal uterus?

The uterus (womb) is a pear-shaped organ, tucked away in your pelvis. It is 7.5cm long, 5cm wide and 2.5cm deep. Inside, it is hollow with thick, muscular walls. The lower third of the uterus dips down into the vagina and is called the cervix. The upper portion is called the fundus and this is where the fertilised egg grows into a baby. Two fallopian tubes, each connected to an egg-filled ovary, enter your uterus on either side at the top.

The uterus leans forwards over the top of the bladder. Doctors call this position anteverted or anteflexed. Some women have a tilted uterus or retroverted uterus. This means it leans away from the bladder rather than over it. It's not strictly speaking an abnormality, because it affects the position, rather than the structure, of the uterus.

About one in six women have a tilted uterus (Haylen et al 2007, Rizk et al 2005). If you're told you have one, it won't affect your chances of getting pregnant. The ability of the sperm to get to your fallopian tubes via your uterus has nothing to do with its position.

What is an abnormal uterus?

A small number of women have a uterus that differs from the norm in structure, rather than position. This is called an abnormality of the uterus, or uterine abnormality. It is a bit of a catch-all phrase, and the numbers reflect this. In the general population, it's thought that somewhere between one woman in 100 and one woman in 20 has a uterine abnormality (Chan et al 2011a, b).

It's also hard to pin down numbers because only some women will have their abnormality identified. In women who seek help for infertility, the rates of uterine abnormalities are estimated to be up to one in 13 women (Chan et al 2011a,b). While in women with a history of late miscarriage, the rates are higher still at up to one in three women (Chan et al 2011b, RCOG 2011).

Will I be able to get pregnant if I have an abnormal uterus?

It depends on the abnormality. But, generally speaking, uterine abnormalities do not affect your ability to become pregnant. You may not even realise you have an abnormality.

Once you're pregnant, it will be seen on an ultrasound scan. Depending on the abnormality, it may make it more difficult for you to carry your baby for the full nine months of pregnancy. Doctors put uterine abnormalities into these categories:

Agenesis

This is extremely rare. It's thought to affect between one woman in 4,000 and one woman in 10,000 (ACOG Committee on Adolescent Health Care 2006). It happens when the vagina does not form properly, or is very short. There may be a very small uterus or none at all. This is usually picked up when a girl doesn't start her periods.

When the time comes, it can also make sex very uncomfortable. The condition can be treated with surgery, and if you have agenesis of the uterus, you should be offered counselling, too. The only way for a woman with agenesis to have a baby is by surrogacy.

Uterus didelphys
This is when the uterus has two inner cavities. Each cavity may lead to its own cervix and vagina, so there are two cervixes and two vaginas. It is uncommon, affecting about one in 350 women (Chan et al 2011a). It is possible to conceive if you have this type of abnormality, and have a straight forward pregnancy (Chan et al 2011b).

Unicornuate uterus
A unicornuate uterus is half the size of a normal uterus and there is only one fallopian tube. Because of its shape, it is described as a uterus with one horn. It is a rare abnormality, affecting about one in 1,000 women in the general population (Chan et al 2011a). It develops in the earliest stages of life, when the tissue that forms the uterus does not grow properly. If you have a unicornuate uterus, you probably have two ovaries. Only one will be connected to your uterus, though. As long as there is one, healthy, developed horn, it is perfectly possible to conceive. However, it does put you at greater risk of miscarriage (Chan et al 2011b).

Bicornuate uterus
Instead of being pear-shaped, this type of uterus is shaped like a heart, with a deep indentation at the top. It is called a uterus with two horns, because of its shape. It's thought that fewer than one in two hundred women in the general population have a bicornuate uterus (Chan et al 2011a). It shouldn't affect your fertility, but you have a higher risk of miscarriage if you do conceive (Chan et al 2011b).

Septate uterus
This is where the inside of the uterus is divided by a muscular or fibrous wall, called the septum. About one in 45 women in the general population have a septate uterus. The septum may extend only part way into the uterus (partial septate uterus) or it may reach as far as the cervix (complete septate uterus). Partial septates are more common than complete septates. A septate uterus may make it more difficult for you to conceive and may increase your risk of miscarriage (Chan et al 2011b).

Arcuate uterus
This looks more like a normal uterus, except it has a dip, or slight indentation at the top. It is a common abnormality, affecting about one in 25 women in the general population (Chan et al 2011a). It.doesn't usually make conceiving difficult (Chan et al 2011b).

How will I know if I have an abnormal uterus?

If you are having fertility problems, your doctor will refer you to a specialist to see if it has anything to do with your uterus or fallopian tubes. There are various investigations that can be carried out:

An 3D ultrasound scan of your uterus may identify an abnormality.

A magnetic resonance imaging (MRI) scan may be used. This is considered to be the best way of scanning for abnormalities. MRI scans use strong magnetic fields and radio waves to produce a detailed image of the inside of your body. This type of examination will only be used if you and your doctor are sure you are not already pregnant.

A special X-ray using dye, called a hysterosalpingography, may be carried out. Liquid containing the dye is flowed into your uterus and fallopian tubes via a fine tube (catheter). This will give your doctor a picture of how well your uterus and fallopian tubes are working.

A minor operation called a laparoscopy may be advised. This allows your doctor to have a look at your uterus and fallopian tubes. Your doctor will perform a small cut in your belly button. He will then pass a tube with a camera (endoscope) through the cut to examine you internally.

How are uterine abnormalities treated?

Not all abnormalities need treatment. Some can be treated, but the treatment itself can carry risks. For example, if you have a septate uterus, one of your options is surgery to have the septum removed. If you have surgery to open your uterus, the lining of your uterus may be damaged. This can reduce your fertility.

It is possible to remove a septum using an instrument called a hysteroscope. A hysteroscope is a thin, telescope-like device that is placed into your uterus via your vagina and cervix. It does far less damage to your uterus than open surgery but it has not been shown to increase the rate of pregnancy in women with infertility (NCCWCH 2013:186).

Comments

I have had 2 miscarriages one at 1 month and one at 2 months the first miscarriage my baby didnt have a heartbeat and the second miscarriage my baby failed to grow so the sac was growing on its own. I found out i have a bicournuate uterus and ive been trying again to have a baby but so frightened im not going to be able to have children and that all im going to do is have another miscarriage just need some support or advice on this?

my first pregnancy ended in a silent miscarriage at ten weeks and I opted to have surgery. At the ultrasound scan it was noticed that my uterus had two cavities and could be bicournate. One radiographer said it looked like there was a dip at the top but could not say if it was definitely bicournate. I have asked for further investigation and am willing to pay but there seems to be little knowledge in Wales. Can anyone suggest specialists in London, that would give me a more definite diagnosis as from reading it could also be septate? Many thanks x

I just had my first first miscarriage (first pregnancy) at 6 weeks. I am about to have my second period since my d&c this coming week and then my husband and I will start trying again. I am terrified! My doctors are suspecting that I have a bicornuate uterus. Is there anyone else out there with a similar story and has gone on to have a healthy pregnancy?

Hi am 5 weeks pregnant. my doc is suspecting tat i may have bicorunate uterus. she advised me for an another usg outside. already one year back i had an miscarriage. am so worried now. will this type of uterus affect my pregnancy?

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